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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
The onset of warps in Spitzer observations of edge-on spiral galaxies
Monthly Notices of the Royal Astronomical Society, Volume 396, No. 1, Year 2009
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Description
We analyse warps in the nearby edge-on spiral galaxies observed in the Spitzer/Infrared Array Camera (IRAC) 4.5-μm band. In our sample of 24 galaxies, we find evidence of warp in 14 galaxies. We estimate the observed onset radii for the warps in a subsample of 10 galaxies. The dark matter distribution in each of these galaxies are calculated using the mass distribution derived from the observed light distribution and the observed rotation curves. The theoretical predictions of the onset radii for the warps are then derived by applying a self-consistent linear response theory to the obtained mass models for six galaxies with rotation curves in the literature. By comparing the observed onset radii to the theoretical ones, we find that discs with constant thickness can not explain the observations; moderately flaring discs are needed. The required flaring is consistent with the observations. Our analysis shows that the onset of warp is not symmetric in our sample of galaxies. We define a new quantity called the onset-asymmetry index and study its dependence on galaxy properties. The onset asymmetries in warps tend to be larger in galaxies with smaller disc scalelengths. We also define and quantify the global asymmetry in the stellar light distribution, that we call the edge-on asymmetry in edge-on galaxies. It is shown that in most cases the onset asymmetry in warp is actually anticorrelated with the measured edge-on asymmetry in our sample of edge-on galaxies and this could plausibly indicate that the surrounding dark matter distribution is asymmetric. © 2009 RAS.
Authors & Co-Authors
Saha, Kanak
India, Bengaluru
Indian Institute of Science
Taiwan, Taipei
Academia Sinica, Institute of Astronomy and Astrophysics
De Jong, Roelof S.
United States, Baltimore
Space Telescope Science Institute
Holwerda, Benne Willem
South Africa, Cape Town
University of Cape Town
Statistics
Citations: 23
Authors: 3
Affiliations: 4
Identifiers
Doi:
10.1111/j.1365-2966.2009.14696.x
ISSN:
00358711
e-ISSN:
13652966